This map should terrify us all

 

Australia, get used to horrific bushfire seasons that rage at greater intensifies and for much longer periods of time.

A joint report released by the Bureau of Meteorology and CSIRO has painted a stark picture of our dramatically changed climate, including more extreme heat days and less rainfall.

And according to the biannual State of the Climate analysis, things are only set to get much worse.

Karl Braganza, manager of climate monitoring at the Bureau, said the occurrence of potentially catastrophic "fire weather" would be more frequent in the future for a number of reasons.

"Fire weather describes maximum daytime temperature, wind speed, humidity and the state of the fuel, so things like drought affect fire indices," Dr Braganza said.

"What we can see is a clear shift towards a lengthened fire season, more fire weather during the season, and that fire weather has become more severe. We see it broadly across most of the continent (but) there are some parts where the fire season has lengthened by months."

The trend has been gradually observed since 1950 but has escalated over the past few decades and poses significant risks to the country.

Fire weather experienced in what would normally be 'shoulder periods' of the typical season - spring and autumn - best highlights the shift, Dr Braganza said.

"Often the worst fire weather occurs when you've had long-term drought, long-term above average temperatures, maybe a short term heatwave … it's those that'll be most challenging going forward in terms of adapting to climate change."

 

This map plots the extent of rainfall declines across Australia.
This map plots the extent of rainfall declines across Australia.

 

Helen Cleugh, the director of the Climate Science Centre at the CSIRO, said Australia is already experiencing climate change now and its impacts are being felt "across many communities and many sectors".

The report showed that the country is more than one degree warmer since records were first kept in 1910. As well as a spike in the number of extreme heat days, observations found that oceans around Australia are warning, contributing to a rise in sea levels, Dr Cleugh said.

"Our observations suggest that in recent decades, the rate of sea level rise has accelerated and it has implications for infrastructure, coastal regions, erosion and so forth," she said.

"Around Australia's coastline, you can see (some levels) are increasing at a rate similar to the global average, but some off the southeast and the north are higher."

 

The number of extreme heat events has increased sharply.
The number of extreme heat events has increased sharply.

 

Warmer waters is leading to an increase in the occurrences of "marine heatwaves" - the consequences of which were seen in 2016 and 2017 with back-to-back coral bleaching events in the Great Barrier Reef.

A southward migration of tropical and subtropical fish illustrates how usually colder waters are warming.

 

Oceans around Australia are getting warmer, the report found.
Oceans around Australia are getting warmer, the report found.

 

Sea levels around Australia are rising on par with international comparisons, although in some areas increases are greater.
Sea levels around Australia are rising on par with international comparisons, although in some areas increases are greater.

 

The combination of reduced rainfall - down 20 per cent since 1970 - and higher temperatures will see extended periods of drought become more common, she said.

By looking at average temperatures since 1910, Dr Braganza said meteorologists analysed how many times per year the mercury hit the warmest one per cent of days on record.

"You can see there were a number of years when we didn't register a single day in that (range) but as we get into the last 20 years, it becomes rarer," he said.

Since 2013, there have been nearly 30 of those extreme heat days, or a five-fold increase.

The State of the Climate report draws on the best available analyses, research and data from an array of evidence-based sources to "provide the best possible information to help manage and adapt to changing climate risk", Dr Cleugh said.


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